Sample steps to manually update Xcode to latest 10.2 version (not necessary once the Xcode 10.2 GA version image has been released on CircleCI)

config.yml

version: 2
jobs:
  build:
    macos:
      xcode: "10.2.0"
    steps:
      - run:
          name: Update Xcode to latest 10.2 version
          command: |
            # Requires setting the XCODE_INSTALL_USER and XCODE_INSTALL_PASSWORD
            # environment variables
            # See: https://github.com/xcpretty/xcode-install#usage
            xcodebuild -version
            sudo gem install xcode-install
            xcversion uninstall 10.2
            xcversion update
            xcversion install 10.2
            xcodebuild -version
          # Expect this to take at least 20 minutes
          no_output_timeout: 60m
workflows:
  version: 2
  build-and-deploy:
    jobs:
    - build